The present invention relates to the creation of digital video effects, and more particularly to an adaptive architecture for video effects that allows a digital video effects (DVE) system to be inserted into multiple points of a video path of a production switcher.
Digital video effects systems have been used together with post production switchers for many years. When used together these two devices can perform complex visual effects. The DVE system is used to enhance the visual effect capability of the production switcher by allowing an image to be spatially transformed, such as by an increase/decrease in size, a change in on-screen location, rotation, perspective change, etc. The production switcher then is used to combine the transformed image with other video signals. This allows such effects as flying a compressed image over a background image, shrinking an on-screen picture to a vanishing point to reveal another image underneath it, compressing and re-positioning a graphic to fit it properly with other visual elements of the picture, and many more.
Historically system timing requirements have meant that the production switcher and DVE system could only be connected in a single, fixed topology, since in order for these two devices to work together effectively very strict timing requirements must be met. If the production switcher combines images that do not meet these timing requirements, unacceptable shifts in on-screen position and color hue destroy the illusion that the visual effect was meant to create. Achieving a particular topology often includes the use of external delay lines and careful alignment of timing adjustments on the DVE system to meet the timing requirements. Some topologies are easier to achieve than others. Often the choice of a particular topology is forced on the system designer by the characteristics of the equipment used and the general system layout of the studio.
The unfortunate result of operating with a single, fixed topology is that some visual effects are easy to obtain, while others are very difficult. The fixed topology means that the transformed image from the DVE system can only appear in certain layers of the composite effect that the production switcher is producing. With large production switchers having two or more mix effects banks that are capable of seven or more simultaneous layers of video in the composite effect, this limitation is generally not cumbersome since the DVE system may be made to appear on intermediate layers, leaving the operator freedom of choice in using the remaining layers that are above or below the DVE system layer in priority. On smaller, single mix effects switchers, which may provide only two or three layers, a fixed topology leaves no flexibility whatsoever. Many visual effects, even though they require only two layers, cannot be achieved in a single pass. Instead they require multiple passes using videotape machines to replay into an upstream layer a portion of the effect that was produced using different layers on a previous pass. These operations are time-consuming and degrade image quality.
What is desired is a flexible topology for the combination of a DVE system with a production switcher, particularly a single mix effects production switcher, so that a transformed image may be inserted into several points of the video path through the production switcher to achieve previously difficult to obtain visual effects.